1. Combined Effect of Age and Severity on the Risk of Dementia in Parkinson's Disease Levy, Gilberto; Schupf, Nicole; Tang, Mingxin; Cote, Lucien J.; Louis, Elan D.; Mejia-Santana, Helen; Stern, Yaakov; Marder, Karen 2002 Articles NeurologyDementiaParkinson's diseaseAging